Exhaust gas recirculation control device of internal combustion engine

Abstract

Providing an exhaust gas recirculation control device of an internal combustion engine by which overshoots or undershoots of an EGR control valve can be prevented, and the tracking performance as to target openings as well as the reliability of the device can be enhanced based on simple control logic. An exhaust gas recirculation control device, being provided with: a feedback control unit 51, and a feed-forward control unit 57, wherein the device is provided with: an adder 73 which adds a feed-forward control command signal 57 to a feedback control command signal 65; and a maximum selection function-section 77 which compares an added value obtained by the adder 73 with a feed-forward control command signal 57 or a command signal from an EGR valve maximum opening map, and selects the command signal by which the valve opening of the EGR control valve is brought to a closed side, wherein the command signal by which the valve opening of the EGR control valve is brought to an opened side is not outputted.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the InventionThe present invention relates to an exhaust gas recirculation device of an internal combustion engine.[0002]2. Background of the InventionAs a measure to reduce NOx emission from an internal combustion engine, it has been a conventional practice to provide the internal combustion engine with an EGR (Exhaust Gas Recirculation) device.[0003]Thereby, an EGR gas control valve for controlling the flow rate of an EGR gas is conventionally provided in an EGR gas passage which connects an exhaust gas passage to an intake air passage; the opening of the EGR control valve is controlled by a feedback correction device so that the opening of the EGR control valve follows a target opening that is determined in response to the operation condition of the internal combustion engine.However, in a transient operation condition, it is not always possible to perform the operation under a pertinent target opening condition. In a case where the ta...

AI Technical Summary

Benefits of technology

[0046]According to the present invention, the overshoot of the EGR control valve opening relative to the target valve opening can be prevented; the smoke generation due to the excessive opening of the EGR control valve can be prevented; and the tracking performance as well as the reliability of the EGR control valve can be enhanced.Further, the feedback control command signal and the feed-forward control command signal are computed in response to the operation conditions of the internal combustion engine. Thus, by intentionally changing and setting the feedback control target signal for computing the feedback control command signal, for instance, by setting the data of a feedback control target map at a data which is intentionally changed from a desirable data in a case of a low load operation range, the selection unit can be set so as to select only the feed-forward control command signal in the low load operation range. In this way, with simple control logic, the change-over between the control only by the feed-forward control command signal and the control by the aggregation of the feed-forward control command signal and the feedback control command signal can be performed.

Problems solved by technology

Thus, there arises a problem that the processes of the control flow to be executed become complicated.

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